I understand the reason for the deaths and Jun leaving but it doesn't make them any less absurd. Jun leaving is unneccesary and happens suddenly. Carter tells him to escort Halsey and he agrees and then thats it. Its basically saying, "Hey! Remeber Jun? He doesn't matter anymore!" and nobody in Noble seems to care either. Kat's death was the most sudden and unexpected of all. She is headshotted through a hole in the roof. The rest of Noble had passed that hole alraedy and the Jackal didnt shoot. Then it kills Kat. Its a stupid and pointless death. It screams to me that Bungie hadn't really thought out her death and just decided anything would do just to get her out of the way. Carter flies the Pelican into the Scarab for no reason. Instead of distracting/fighting the Scarab he decides suicide is the only way. It tries to be a big emotional moment but it ends up being a dull and un-needed death. Jorge's sacrifice was the one death that made sense in the game. He thought he was destroying the Covenant's main force and it was a huge event in the War. But then, more carriers show up and negate the whole point. It was so dissapointing. It was a heroic deed for, maybe, 20 seconds and then was made useless. Emile, who has a radar, stands there and doesn't react to an Elite who casually walk up behind him and stabs him. Once again, says to me that Bungie thought anything would do. I don't mind if their deaths were lacklustre so much but they could have been much more meaningful and actually made sense.
Indeed, reality, doesnt work that way. Many soldiers die suddenly with absolutely no heroism to it. But we don't make stories and video games following the story of a random soldier who died from a stray bullet. Were talking about a completely fictional universe whose content is used to entertain. Seeing the demise of Noble Team failed to entertain. It tried to make you care about dull and boring characters with dull and stupid deaths. Their deaths can be mundane. For example, Kat's death would have made sense if the Team was under fire at any stage beforehand and she was killled while the Team was running for cover. Then again, the majority of people play Halo to be entertained so "Hollywood" deaths would have been a much better and interesting route to take the story.
How is Jun leaving unnecessary? Would it make sense to leave the universe's most intelligent human to leave unescorted? No. Halsey is far too valuable, especially back then. And how would you expect remains of Noble Team to 'care' exactly? You think some of humanity's finest fighters are going to have a sad moment saying goodbye to Jun as he simply goes to escort Halsey? That would be comical. Imagine a soldier or marine today giving an order to escort civilians away from a warzone to another soldier, you think the whole platoon's gonna stop and say bye to them for their [hopefully] temporary leave? Of course Jun will agree, and of course someone has to take care of Halsey. You follow orders made by your commander, unless they're completely irrational and will only hurt the objective - but even then many would still follow those orders.
The phantom in which the Elite sniper was aboard may have been mobile, and this is highly likely considering if it was stationary the whole time, Noble would have noticed it. The phantom was cruising, stopped as they saw Noble Team run by, and the sniper took a shot. Kat, or who ever's at the back, is more likely to get shot because they are closer to the sniper. Makes sense. Why go for a harder target? The Elite picked the Spartan who'll most likely receive a fatal shot, and he fired. It was Kat because she was furthest behind. Not only would a target further in front be harder because of distance, but they'll also have other Spartans running behind them and getting in the way. Kat was unfortunately the most convenient shot for the sniper. A needler round in the head, which then explodes, would be a very quick death. It's one pretty big hole as well. The Covenant have a policy of wanting us all dead, they're aware of Spartan activity in the area, so I'm sure they could spare some dropships to kill at least one.
So you think Carter's gonna give the scarab a few pokes whilst Emile and B312 stand and watch for half an hour? Carter was wounded badly, and may have died anyway considering he couldn't receive any medical attention. Why just lay the Pelican down and die when he could actually make the mission a success and get Emile and B312 across that scarab. Yeah, if he was in good health you may have a point, but he really wasn't. Scarabs don't go down that easily, without heavy firepower (and I mean real heavy), we all know the only way is getting inside one of them.
You're spot on about Jorge, sad really, but he certainly made a difference as mentioned above.
When in combat, it's best to actually look at the enemy you're killing instead of your radar. Emile was stabbed straight after finishing off an Elite. Nothing too casual about how the zealot approached him, the phantom dropped off multiple zealots which swarmed the platform. He took out one and got killed by another behind him, you don't engage in combat whilst monitoring your radar. Search into flight-or-fight responses and the sympathetic nervous system.
These deaths make perfect sense, and most deaths aren't meaningful unfortunately. As we said above and you clearly acknowledged, reality isn't always like that. Maybe most people don't produce media about a 'random soldier who died from a stray bullet', but Bungie did, and many thanks to them for that. Stereotypically any 'sci-fi' media is considered unrealistic, but what most people appreciate about Halo is its realism. Look into the lore and you'll realise it mirrors modern-day life so similarly, it's sometime hard to identify a difference. I'd rather face realism that anything that's done just to entertain the masses. It's best for Halo to stay grounded into reality, though that's happening less now that the Forerunners/Prometheans are more involved, but even with them Halo does a great job of providing a plausible scientific explanation.
If there's anything I mentioned which you have any questions about or disagree with, please let me know.